Hi aman, first of all welcome to Webforumz! You don't need a whole lot in terms of software packages to get started. I assume you will be handcoding your sites? Are you already familiar with using (x)
html and
css? If so, you just need something like notepad to code it in. If you want something with a few more features, there are several choices and people have their own favourites - I use Text Wrangler which is free to download, but quite a few on here use Dreamweaver (in code view of course!), but there are many others.
Aside from that you'll need something for graphics if you haven't got that already, I use Photoshop as do many others, I have also seen Fireworks recommended a fair bit on here. Or you can download Gimp for free - I had a few problems with Gimp myself when I used it, but I know there are some on here who get on well with it.
That's all you really need to get started - somewhere to write your code and somewhere to create/edit graphics.